fuel pump blues ?

[Al]

My 1968 Charger has recently developed a dislike for cold starting. It starts very fast but then after 20 seconds starts to run uneven, rpm goes down and when put in gear the engine dies. After about 5 minutes of idling everything's fine.

When I start cold my fuel pressure gauge fluctuates very rapidly from 0 to 4 psi, after 5 minutes of idling the gauge stays steady at around 3.8 psi .

It is a real p ... in the ... to get the thing started. By the way the Charger has a 383 with new MSD 6 box, now MSD coil and new MP dizzy and a new Holley Street Avenger 670, new fuel filter, new spark plugs ...  Timing is 15 deg @ 800 rpm vacuum disconnected. Electrical choke, tried different positions from 0 notches to +2 and -4, to no avail.

Is the fuel pump the culprit?  

Al

[firefighter3931]

Hi Al, from what you are describing it sounds like vapor lock/fuel evaporation....if the fuel pump was bad it would read low all the time.

Often what happens is the fuel will evaporate if the car sits for a few days then the pump has to refill the bowls.

This is only a cold start problem correct ? If the engine is warm does the fuel pressure still read low on start-up ?



Ron

[Al]

Yes only a cold start problem Ron. But the car didn't do it with my old AVS and with the new Holley only recently.  

Al

[firefighter3931]

Yes only a cold start problem Ron. But the car didn't do it with my old AVS and with the new Holley only recently.  

Al

I'm thinking it's a fuel evaporation issue Al.  Keep an eye on it for now and if it continues to happen on warm re-starts then we can explore other options. One thing you can do to help is to install a carb base insulating gasket....this will keep the carb and fuel cooler and slow down the fuel boiling & exaporation.


Ron

[Al]

Ok Thanks Ron. I'll get a phenolic spacer to replace my aluminim carb spacer and a carb base insulating gasket when I'm back.

Kind regards  
Al

[firefighter3931]

Ok Thanks Ron. I'll get a phenolic spacer to replace my aluminim carb spacer and a carb base insulating gasket when I'm back.

Kind regards  
Al

Al, you don't need to replace the aluminum spacer as long as you go with the thick base gasket. The phenolic spacer works as well with regular thin base gaskets but you don't need to use both. 



Ron

[Al]

Ron would this one be ok ?

http://www.summitracing.com/parts/HLY-108-37/?image=large

Al

[firefighter3931]

Ron would this one be ok ?

http://www.summitracing.com/parts/HLY-108-37/?image=large

Al

Al, that one is for a spreadbore carb (small primaries/large secondaries >  Thermoquad). You need one for a squarebore (standard Holley)....unless you have a spreadbore holley carb.

What carb are you running ? What intake manifold ? Is your spacer open or 4 hole design ?



Ron

[Just 6T9 CHGR]

Could it also be a worn fuel pump pushrod?  I was having a similar prob about 10 years ago.....turned out the pushrod was worn down 3/4"..... Enough to pump some fuel but starve under load or heat

just a thought

[Al]

It's a brand new Holley Street Avenger 670 with electrical choke. The spacer is a 4 hole 0.5 inch on an Eddy RPM intake and KN drop base air cleaner. And the problem only manifests itself 20 seconds after startup for about 5 to 8 minutes. If I put in D or R the engine dies. Then after idling for about 5 to 8 minutes the engine runs fine.  

@Ron : Would this one be ok? http://www.summitracing.com/parts/MRG-758/
@NOT Just 6T9 CHGR: No problems under load on acceleration or at higher speed

Al  

[firefighter3931]

@Ron : Would this one be ok? http://www.summitracing.com/parts/MRG-758/
Al  

Yep, that is perfect....mount it between the carb and spacer. 


Ron


Ps. Just69 makes a good point about the fuel pump pushrod....they do wear out. I just don't think that this is your problem. The fact that it runs fine after warmed up points to other issues.

[b5blue]

Could his choke need adjusting? 

[Al]

Could his choke need adjusting? 

Neal The carb has an electrical choke. My first thought was also the choke adjustment. So I tried different positions from 0 notches to +2 and -4 : it has no influence on the problem. 

Al

[b5blue]

Got ya....odd pain in the butt problem! 

[Al]

Got ya....odd pain in the butt problem! 

yep

Al

[b5blue]

How long did it run good with the Holley?

[Al]

A few weeks. However I only drive the car on weekends and when the weather is fine.

Al